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Diagnosis of Colon Cancer

Symptoms, Identification and Staging

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Updated April 09, 2014

Do you have blood in your stool? Check. Fullness, bloating, and excess gas? Check, check, check. You could potentially have every symptom indicative of colon cancer -- but that doesn't mean you have colon cancer. Making the leap from symptoms or a family history to a diagnosis requires tests to verify the presence of cancerous cells, followed by more tests to identify if the cancer is localized in the colon or if it has spread (metastasized) to other areas in your body.

A diagnosis of colon cancer may come as a complete surprise following a routine screening exam, such as a colonoscopy, without the presence of any symptoms.

What to Expect at Your Initial Visit

Following a positive screening exam or the presence of concerning symptoms, your doctor will schedule a diagnostic workup for colon cancer. He or she will obtain a thorough medical history and examination that may include a digital rectal exam. This simple, painless test allows the doctor to check your rectum for any growths or masses. The doctor may also collect a stool sample for a fecal occult blood or immunochemical test, which identify trace amounts of blood in the stool. Your doctor may order further testing, such as:

  • Blood tests, including a complete blood count, clotting times (especially if you take blood thinners) and an electrolyte panel, help your doctor form a picture of your general health. If you have a history of cancer, the doctor may also order a carcinoembryonic antigen (CEA) test, which can help identify if tumors have returned.

  • Diagnostic imaging tests use different forms of x-rays to see your colon and surrounding tissues. These tests are usually painless and can include x-rays, computed tomography (CT) scans, magnetic resonance imaging (MRI), or rectal ultrasounds. The doctor may order a contrast agent, such as barium, to be given orally, rectally or in an intravenous line before the picture is taken. Contrast agents make your colon more visible -- like turning on the lights when you enter a dark room.

  • Colonoscopy and sigmoidoscopy are procedures that use a small, lighted probe with a camera, inserted through your rectum, to see inside your colon and rectum. If the doctor finds polyps or unhealthy tissues in your colon, he or she can take a biopsy during the procedure.

  • A biopsy refers to any time the doctor takes a tiny sample of tissue from your body. Colon biopsies can be completed during colonoscopies, sigmoidoscopies or during a CT scan-guided needle biopsy. A pathologist, or a special doctor who can differentiate between cancerous and non-cancerous cells, carefully examines the tissue samples. Biopsy results can take from 72 hours up to a week for processing. Ask your doctor when to expect results.

It's Colon Cancer, Now What?

You will be asked to come back to the doctor's office to discuss your test results and diagnosis. Consider bringing a family member or trusted friend to this visit -- he or she can provide support and another set of ears.

Once a diagnosis of colon cancer is made, the next step involves finding out if the cancer has spread (metastasized) to other parts of your body. This process, also known as staging the cancer, will require a few more tests before you can move forward to treating the cancer. The most common sites for colon cancer metastasis include the lungs, liver and the peritoneum, or the abdominal lining. Your doctor may order a:

  • Chest x-ray to make sure your lungs are clear and free of metastasis
  • Abdominal ultrasound to see if the cancer has spread to sites in your abdomen, such as the liver, stomach or peritoneum
  • Positron emission tomography (PET) scan to take a look for cancerous growths within your entire body

Colon Cancer Staging Tools

There are two ways to stage the spread and severity of cancer: clinical and pathological staging. Clinical staging is the process by which your doctor compares the test results with your physical presentation. Pathologic staging, which is more accurate, uses three systems to represent the extent of disease progression. These systems include:

  • American Joint Committee on Cancer Staging System (TNM)
  • Astler-Coller
  • Dukes

Out of the three, the TNM system is the most widely used system for staging colon cancers. The three letters are used to stage the size of the tumor (T), spread to lymph nodes (N), and the extent of metastasis (M). Each letter is followed by a descriptor, usually a number, which will describe the severity of your colon cancer. Lower numbers, such as a 0, are desirable in staging as they signify that the cancer is small and localized (in situ).

Another term you will come across is called grading the tumor. When the pathologist identifies cancerous cells, he or she can also determine how mutated those cells appear, or how abnormal the cancerous tissue appears compared to regular tissue. Similar to staging, cancers with a lower grade (a more normal appearance) are usually found early and are easier to treat, whereas very mutated or high-grade cancers have a higher probability of spreading quickly.

Treatment Plan

Your doctor will work with you to form a treatment plan for the colon cancer, which may include surgery, chemotherapy, radiation or a combination of treatments. Your plan will be tailored for your specific needs, but is largely based on the grade and stage of the cancer and your overall physical health.

Sources:

American Cancer Society. (2008). Colorectal Cancer. What You Need to Know - NOW. Atlanta: American Cancer Society Health Promotions.

National Cancer Institute. (2011). Metastatic Cancer. Accessed: November 3, 2011.

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